HSV-2 is the primary cause of infectious ulcerative genital disease worldwide, with HSV-1 becoming an increasingly important cause of genital herpes infection. Worldwide there are an estimated 23 million new HSV-2 infections per year. A number of HSV-2 vaccine approaches have been tested in the clinic (reviewed by Johnston C, et al., J Clin Invest 2011, 121:4600-4609) with varied degree of success. To address the lack of an effective vaccine, a replication defective HSV-2 vaccine strain virus (dl5-29, which has since been re-derived and renamed ACAM529 (Delagrave S, et al. PLoS ONE, 2012 7(10): e46714), also known as HSV529) has been constructed by deleting the UL5 and UL29 genes from the wild type virus (Da Costa X, et al., J Virol 2000, 74:7963-7971). The vaccine strain virus dl5-29 induces a protective immune response in vivo in mice and guinea pigs without either replication or establishment of latency (Da Costa X J, et al., Proc Natl Acad Sci USA 1999, 96:6994-6998; Hoshino Y, et al., J Virol 2005, 79:410-418; Hoshino Y, et al., J Infect Dis 2009, 200:1088-1095). Additionally, dl5-29 was shown to be effective in prevention of latent infection in guinea pigs irrespective of HSV-1 serostatus (Hoshino Y, et al., J Infect Dis 2009, 200:1088-1095). However, these studies were carried out with vaccine purified using centrifugation-based methods which are not readily scaled for commercial production. Indeed, a number of groups have defined laboratory-scale procedures for purification of herpes viruses based upon centrifugation (Arens M, et al., Diagn Microbiol Infect Dis 1988, 11:137-143; Lotfian P, et al., Biotechnol Prog 2003, 19:209-215); gradients (Goins W F, et al., Methods Mol Biol 2008, 433:97-113; Sathananthan B, et al., APMIS 1997, 105:238-246; Sia K C, et al., J Virol Methods 2007, 139:166-174; Szilagyi J F, et al., J Gen Virol 1991, 72 (PT 3):661-668); filtration (Knop D R, et al., Biotechnol Frog 2007, 23:715-721); and affinity chromatography (Jiang C, et al., Biotechnol Bioeng 2006, 95:48-57; Jiang C, et al., J Virol 2004, 78:8994-9006).
As with centrifugation-based methods, these other traditional laboratory-scale purification processes for vaccine strain viruses involve laborious procedures that cannot be scaled for commercial production of viral compositions prepared in accordance with World Health Organization (WHO) guidelines for human use, resulting in either low yields or insufficient purity (e.g., excessively high levels of residual host cell DNA). The World Health Organization (WHO) provides an upper limit of 10 ng host cell DNA per human dose, thus a need exists to provide virus preparations with less than 10 ng host cell DNA per human dose.